Saturday, 30 March 2013

Wireless Backhaul and Vendor Landscape

While some people forecast that as many as 80 or 90% of outdoor metrocells will be connected by wireless backhaul, Maravedis-Rethink believes we'll see something closer to today's split in macrocells - about 55% wireless and 45% fiber. Operators will use fiber wherever possible and install short range wireless in the gaps.

In some countries, the availability of fiber is far higher than in others, for example in South Korea, China and Japan. Even in the US, where there is plenty of copper, my guess is that operators will try to reuse existing copper lines to reach the nearest fibre point of presence. As an analyst, it would be quite easy to be aggressive with high wireless backhaul forecasts, but we have to consider that in reality most operators are very conservative about adopting new technology.

So wireless backhaul may be more important for metrocells than for macrocells, but not excessively so.The most important issue for a metrocell is to offload traffic from the macro network. Location is fundamental – the NGMN (Next Generation Mobile Network) Alliance has indicated that cells need to be located within 10 meters of each traffic hotspot – so there really needs to be far more flexibility in backhaul. This is where wireless backhaul becomes more significant.

The role that third party players offering ‘small cells as a service’ such as Virgin and Colt can play is also important. The value of street furniture will increase in the coming years. Those who deployed city Wi-Fi in the past (and failed through lack of monetization) have now realised they were getting access to valuable infrastructure. If you get permission for public Wi-Fi and small cell deployment then that could make the service provider Wi-Fi business more interesting. This gives intermediate players like Virgin, who can deal directly with building, real estate and council owners, an important role to isolate network operators from many/multiple negotiations with location owners. This would make it much more convenient for operators to contract through intermediate players than directly themselves.

Which wireless technology will be most important?

The issue here is less about technology and more about spectrum. In my opinion, the key requirements are the flexibility to deploy without having to wait for regulatory permission or having to deal with interference from other operators. Taking this into account, the main spectrum choices for mobile operators for small cells are between:

a) Availability of block allocated point to multi-point (PMP) spectrum. These are microwave frequencies, licensed exclusively in a given geographical area. For example, in Europe 26 or 28GHz or even 42GHz. 42GHz is interesting because it can use a smaller antenna and there is more spectrum available.

One reason why PMP spectrum is more interesting for metrocells than for macro is that the cells will be positioned at low heights 3-6m above street level. Streets become canyons with good RF isolation between different parallel streets. This leads to much greater spectrum reuse than has been possible before in macro, ultimately allowing the P-MP spectrum to be used more like point-to-point (P-P) because it avoids interference.

Some of the intermediate players may acquire spectrum in these bands. This will be the first place to look for small cell deployment.

b) V-Band (60GHz) is the perfect complement, especially for those who don't own block allocated spectrum. There is plenty of capacity and minimal interference. Spectrum is lightly licensed (effectively free) and the wavelength provides a benefit of small size antennas. This technology perfectly fits small cell backhaul requirements.

By contrast, the E-Band (70/80GHz) requires a larger antenna to meet the regulator requirements of the radiation mask. The larger form factor cannot be quite so easily hidden and integrated into street furniture. Some advances in size reduction are being achieved though, such as E-Band Communications' E-Link Mini.

c) Non-Line-Of-Sight (NLoS). The main challenge here is availability of spectrum, which must be below 6GHz. Some vendors in the industry such as Fastback Networks are promising high capacity also in NLoS conditions, where throughput has traditionally decreased considerably compared to LoS. If capacity is insufficient, then operators can't ensure the quality of experience. So I will be very interested to see what real-world performance these new vendors can achieve and learn how they have surmounted the capacity constraints in sub-6GHz spectrum. Advanced antenna techniques are certainly among the main tools to achieve this.

ThinkSmallCell has compiled an excellent list of Small Cells Wireless Backhaul Vendors here. The list differentiates between different wireless technologies based on the spectrum and which vendors offer solutions for that band.